This is directed to calibrating a motion sensor array. In particular, this is directed to calibrating a three-axis motion sensor in an electronic device.
Electronic devices can include several interfaces or mechanisms for a user to provide inputs to the devices. For example, devices can include one or more buttons, keys, switches, or other physical interfaces. As another example, devices can include one or more touch sensitive surfaces (e.g., a touch pad or a touch screen) by which a user can provide inputs. As still another example, devices can include one or more sensors that can capture information about the environment of a device or the position of the device in the environment. Such sensors can include, for example, a proximity sensor, an ambient light sensor, an infrared sensor, a multi-axis motion sensor (e.g., an inertial measurement unit such as a gyroscope or accelerometer), or combinations of these.
In some embodiments, the output of one or more sensors can be used by an application or device process. For example, the output of an ambient light sensor or of a proximity sensor can be used to turn on or off a display. As another example, the output of an inertial measurement unit can be used to control the orientation of displayed information (e.g., portrait or landscape). As still another example, the output of an inertial measurement unit can be used to control the movement of information provided on a display (e.g., to control a game). As still yet another embodiment, the output of an inertial measurement unit can be used to correct the error in the output of another sensor (e.g., to correct the output of a compass).
The output of an inertial measurement unit, however, may not be oriented in a manner that matches a reference frame of a device in which the inertial measurement unit is placed. In particular, each of three individual sensors can be offset relative one another, and the combined sensors forming the inertial measurement unit can be offset relative to the device axes when the inertial measurement unit is placed within the device. The offset can cause the output of the inertial measurement unit to be inaccurate and adversely affect the operation of one or more device processes or applications.